The present invention relates to a release mechanism for a pyrotechnic item, such as an aircraft parachute flare, and more particularly to a release mechanism which is actuated by fins which first open and then impart a spin to the release mechanism to unlock an inertia arm preventing operation of a timer.
An aircraft parachute flare is normally provided with three sections or components, namely a parachute, a section containing a pyrotechnic composition and a triggering mechanism. The triggering mechanism, in addition to igniting the pyrotechnic composition, frequently provides for a delay period so that the aircraft parachute flare can free fall a predetermined distance prior to parachute opening. This free fall feature permits the aircraft parachute flare to be launched or dropped from relatively high altitudes, but prevents ignition of the pyrotechnic composition until the parachute flare is at an altitude such that light from the flare will illuminate the ground below.
As an aircraft parachute flare is an expendable item, possibly the most important features on these flares are the safety features which attempt to prevent accidental or premature ignition of the pyrotechnic composition. As the illuminating materials which are used in present day flares provide extreme heat upon burning, any accidental ignition of these flares could result in a catastrophic disaster, particularly if the flares are in storage aboard a ship. In order to provide some measure of safety, most present day flares are provided with a safety pin which is kept in position until the flare is mounted in a launching rack on an aircraft. In the event the aircraft returns with flares, the safety pins are reinserted.
In one type of fuze widely used by the military departments, a lanyard is provided and has one end attached to the fuze and the other end attached to the aircraft. Upon dropping the store to which the fuze is attached, the lanyard actuates a triggering mechanism which fires the store. While a lanyard is normally successful in triggering a fuze, it has a disadvantage of sometimes causing an undesired triggering, such as the dropping of a store during landing or taxing of an aircraft. In a carrier landing, for example, an accidental dropping of a flare which is triggered by a lanyard, could cause a serious shipboard fire.
In order to eliminate the need for a lanyard, a fuze was developed for the Navy which is initiated by the environment. This device is shown and described in U.S. Pat. No. 3,780,659, entitled, "Environmental Fuze For Pyrotechnic Device", which issued Dec. 25, 1973, to Stanley Kulesza and Max Sapsowitz. In this device, fuze action is started by a plurality of pressure sensing fins which, upon actuation, initiates a timing mechanism and seals a bellows assembly. The bellows assembly monitors the increase of atmospheric pressure as the fuze falls and, if a predetermined pressure change occurs within a given time period, the firing pin is released to detonate a primer. In the event that the desired pressure change does not occur during a given time interval, the timing mechanism will jam and the fuze will remain in a safe condition.